Jin Dr. J. S. r.olton. 2 t Hbtologicdl Localisation 



" The Exact Histological Localisation of the Visual Area of the 

 Human Cerebral Cortex." By JOSEPH SHAW BOLTON, !' ^ 

 M.D., B.S. (Loncl). Coinnmnicated by Dr. MOTT, F. ! 

 i: .-iveil May 11, Head June 14, 1900. 



(Abstract.) 



Previous Research. 



The previous research concerning the human visual area has l>een 

 carried out in three directions. 



(1) The study of lesions causing blindness. 



(2) The study of the myelination of the corona radiata. 



(3) The histological examination of " occipital " or " calcarine " 

 cortex as regards 



(a) Cell form. 



(b) Subdivision of this variety of cortex into layers. 



(c) The modifications caused in (a) and (b) by long-standing blind- 



ness. 



> Examination of the literature on the first two subdivisions demon- 

 strates the extreme diversity of opinion which exists regarding the 

 situation of the primary visual area of the cortex. 



The object of the present research has been to indicate the exact 

 region of the cortex to which the visuo-sensory function is limited. 

 For this purpose it has been unnecessary to pay attention to the 

 special neuronic structure of this portion of the cerebrum, but the 

 general histology of the cortex referred to in (3), (b), and (c) has been 

 considered minutely in the third section of this paper. 



The Exact Distribution of the " Occipital " Lamination. 



(1) The " occipital " lamination in the region of the calcarine fissure 

 has been histologically mapped out, in six normal and pathological 

 brains, as a well defined cortical area. 



(2) The general distribution of this area is as follows. It occupies 



(a) The body of the calcarine fissure, including the anterior and 



posterior annectants, and extending upwards to the parallel 

 cuneal sulcus and downwards to the collateral fissure. 



(b) The posterior part of the calcarine fissure extending to the polar 



sulci surrounding its extremities. 



(') The inferior lip of the stem of the calcarine fissure (including the 

 superficial surface and lower lip of the cuneal annectant) nearly 

 to its anterior extremity, just posterior to which the area tails 

 off to a sharp point. 



